1. Field of the Invention
The present application relates to wireless networking and, in some preferred embodiments, to methods of improving wireless communications, such as, e.g., for enhanced throughput, for reduced delays, for enhanced range (e.g., distance) of wireless communications and/or the like.
2. General Background Discussion:
Networks and Internet Protocol
There are many types of computer networks, with the Internet having the most notoriety. The Internet is a worldwide network of computer networks. Today, the Internet is a public and self-sustaining network that is available to many millions of users. The Internet uses a set of communication protocols called TCP/IP (i.e., Transmission Control Protocol/Internet Protocol) to connect hosts. The Internet has a communications infrastructure known as the Internet backbone. Access to the Internet backbone is largely controlled by Internet Service Providers (ISPs) that resell access to corporations and individuals.
With respect to IP (Internet Protocol), this is a protocol by which data can be sent from one device (e.g., a phone, a PDA [Personal Digital Assistant], a computer, etc.) to another device on a network. There are a variety of versions of IP today, including, e.g., IPv4, IPv6, etc. Each host device on the network has at least one IP address that is its own unique identifier.
IP is a connectionless protocol. The connection between end points during a communication is not continuous. When a user sends or receives data or messages, the data or messages are divided into components known as packets. Every packet is treated as an independent unit of data.
In order to standardize the transmission between points over the Internet or the like networks, an OSI (Open Systems Interconnection) model was established. The OSI model separates the communications processes between two points in a network into seven stacked layers, with each layer adding its own set of functions. Each device handles a message so that there is a downward flow through each layer at a sending end point and an upward flow through the layers at a receiving end point. The programming and/or hardware that provides the seven layers of function is typically a combination of device operating systems, application software, TCP/IP and/or other transport and network protocols, and other software and hardware.
Typically, the top four layers are used when a message passes from or to a user and the bottom three layers are used when a message passes through a device (e.g., an IP host device). An IP host is any device on the network that is capable of transmitting and receiving IP packets, such as a server, a router or a workstation. Messages destined for some other host are not passed up to the upper layers but are forwarded to the other host. In the OSI and other similar models, IP is in Layer-3, the network layer. The layers of the OSI model are listed below.
Layer 7 (i.e., the application layer) is a layer at which, e.g., communication partners are identified, quality of service is identified, user authentication and privacy are considered, constraints on data syntax are identified, etc.
Layer 6 (i.e., the presentation layer) is a layer that, e.g., converts incoming and outgoing data from one presentation format to another, etc.
Layer 5 (i.e., the session layer) is a layer that, e.g., sets up, coordinates, and terminates conversations, exchanges and dialogs between the applications, etc.
Layer-4 (i.e., the transport layer) is a layer that, e.g., manages end-to-end control and error-checking, etc.
Layer-3 (i.e., the network layer) is a layer that, e.g., handles routing and forwarding, etc.
Layer-2 (i.e., the data-link layer) is a layer that, e.g., provides synchronization for the physical level, does bit-stuffing and furnishes transmission protocol knowledge and management, etc. The Institute of Electrical and Electronics Engineers (IEEE) sub-divides the data-link layer into two further sub-layers, the MAC (Media Access Control) layer that controls the data transfer to and from the physical layer and the LLC (Logical Link Control) layer that interfaces with the network layer and interprets commands and performs error recovery.
Layer 1 (i.e., the physical layer) is a layer that, e.g., conveys the bit stream through the network at the physical level. The IEEE sub-divides the physical layer into the PLCP (Physical Layer Convergence Procedure) sub-layer and the PMD (Physical Medium Dependent) sub-layer.
Typically, layers higher than layer-2 (such as, e.g., layers including the network layer or layer-3 in the OSI model and the like) are referred to as the higher-layers.
Wireless Networks
Wireless networks can incorporate a variety of types of mobile devices, such as, e.g., cellular and wireless telephones, PCs (personal computers), laptop computers, wearable computers, cordless phones, pagers, headsets, printers, PDAs, etc. For example, mobile devices may include digital systems to secure fast wireless transmissions of voice and/or data. Typical mobile devices include some or all of the following components: a transceiver (i.e., a transmitter and a receiver, including, e.g., a single chip transceiver with an integrated transmitter, receiver and, if desired, other functions); an antenna; a processor; one or more audio transducers (for example, a speaker or a microphone as in devices for audio communications); electromagnetic data storage (such as, e.g., ROM, RAM, digital data storage, etc., such as in devices where data processing is provided); memory; flash memory; a full chip set or integrated circuit; interfaces (such as, e.g., USB, CODEC, UART, PCM, etc.); and/or the like.
Wireless LANs (WLANs) in which a mobile user can connect to a local area network (LAN) through a wireless connection may be employed for wireless communications. Wireless communications can include, e.g., communications that propagate via electromagnetic waves, such as light, infrared, radio, microwave. There are a variety of WLAN standards that currently exist, such as, e.g., Bluetooth, IEEE 802.11, and HomeRF.
By way of example, Bluetooth products may be used to provide links between mobile computers, mobile phones, portable handheld devices, personal digital assistants (PDAs), and other mobile devices and connectivity to the Internet. Bluetooth is a computing and telecommunications industry specification that details how mobile devices can easily interconnect with each other and with non-mobile devices using a short-range wireless connection. Bluetooth creates a digital wireless protocol to address end-user problems arising from the proliferation of various mobile devices that need to keep data synchronized and consistent from one device to another, thereby allowing equipment from different vendors to work seamlessly together. Bluetooth devices may be named according to a common naming concept. For example, a Bluetooth device may possess a Bluetooth Device Name (BDN) or a name associated with a unique Bluetooth Device Address (BDA). Bluetooth devices may also participate in an Internet Protocol (IP) network. If a Bluetooth device functions on an IP network, it may be provided with an IP address and an IP (network) name. Thus, a Bluetooth Device configured to participate on an IP network may contain, e.g., a BDN, a BDA, an IP address and an IP name. The term “IP name” refers to a name corresponding to an IP address of an interface.
An IEEE standard, IEEE 802.11, specifies technologies for wireless LANs and devices. Using 802.11, wireless networking may be accomplished with each single base station supporting several devices. In some examples, devices may come pre-equipped with wireless hardware or a user may install a separate piece of hardware, such as a card, that may include an antenna. By way of example, devices used in 802.11 typically include three notable elements, whether or not the device is an access point (AP), a mobile station (STA), a bridge, a PCMCIA card or another device: a radio transceiver; an antenna; and a MAC (Media Access Control) layer that controls packet flow between points in a network.
In addition, Multiple Interface Devices (MIDs) may be utilized in some wireless networks. MIDs may contain two independent network interfaces, such as a Bluetooth interface and an 802.11 interface, thus allowing the MID to participate on two separate networks as well as to interface with Bluetooth devices. The MID may have an IP address and a common IP (network) name associated with the IP address.
Wireless network devices may include, but are not limited to Bluetooth devices, Multiple Interface Devices (MIDs), 802.11x devices (IEEE 802.11 devices including, e.g., 802.11a, 802.11b and 802.11g devices), HomeRF (Home Radio Frequency) devices, Wi-Fi (Wireless Fidelity) devices, GPRS (General Packet Radio Service) devices, 3G cellular devices, 2.5G cellular devices, GSM (Global System for Mobile Communications) devices, EDGE (Enhanced Data for GSM Evolution) devices, TDMA type (Time Division Multiple Access) devices, or CDMA type (Code Division Multiple Access) devices, including CDMA2000. Each network device may contain addresses of varying types including but not limited to an IP address, a Bluetooth Device Address, a Bluetooth Common Name, a Bluetooth IP address, a Bluetooth IP Common Name, an 802.11 IP Address, an 802.11 IP common Name, or an IEEE MAC address.
Wireless networks can also involve methods and protocols found in, e.g., Mobile IP (Internet Protocol) systems, in PCS systems, and in other mobile network systems. With respect to Mobile IP, this involves a standard communications protocol created by the Internet Engineering Task Force (IETF). With Mobile IP, mobile device users can move across networks while maintaining their IP Address assigned once. See Request for Comments (RFC) 3344. NB: RFCs are formal documents of the Internet Engineering Task Force (IETF). Mobile IP enhances Internet Protocol (IP) and adds means to forward Internet traffic to mobile devices when connecting outside their home network. Mobile IP assigns each mobile node a home address on its home network and a care-of-address (CoA) that identifies the current location of the device within a network and its subnets. When a device is moved to a different network, it receives a new care-of address. A mobility agent on the home network can associate each home address with its care-of address. The mobile node can send the home agent a binding update each time it changes its care-of address using, e.g., Internet Control Message Protocol (ICMP).
In basic IP routing (i.e. outside mobile IP), typically, routing mechanisms rely on the assumptions that each network node always has a constant attachment point to, e.g., the Internet and that each node's IP address identifies the network link it is attached to. In this document, the terminology “node” includes a connection point, which can include, e.g., a redistribution point or an end point for data transmissions, and which can recognize, process and/or forward communications to other nodes. For example, Internet routers can look at, e.g., an IP address prefix or the like identifying a device's network. Then, at a network level, routers can look at, e.g., a set of bits identifying a particular subnet. Then, at a subnet level, routers can look at, e.g., a set of bits identifying a particular device. With typical mobile IP communications, if a user disconnects a mobile device from, e.g., the Internet and tries to reconnect it at a new subnet, then the device has to be reconfigured with a new IP address, a proper netmask and a default router. Otherwise, routing protocols would not be able to deliver the packets properly.
Some Limitations of Existing Wireless Systems
This section sets forth certain knowledge of the present inventors, and does not necessarily represent knowledge in the art.
One of the inherent features of a broadcast medium like wireless is that, generally speaking, all stations can listen to all packets, as long as they are within the wireless transmission (e.g., radio) range.
In such wireless communications, when a receiver within the network receives a wireless transmission (e.g., one or more packet), the receiver decodes the destination MAC address identified in the transmission. If the destination address does not match it's own MAC address, the receiver drops the packet without further processing. In this manner, the receiver makes no further use of packets that are not intended for itself.
Generally speaking, in such wireless communications, there can in many circumstances be one or more low speed and/or unreliable communication link(s) (such as, e.g., between a mobile node or other wireless device and an access point), which links can result in, among other problems, 1) low throughput, 2) delays caused by local/temporal interferers, and/or 3) range limitation.
Existing WLAN systems typically have an access point (AP) and a number of stations that are distributed across the radio range of the AP. Due to this spatial distribution of the stations, each station will experience a different link quality to and/or from the AP. If the transmission power and the rate were kept constant, this would translate directly into different link error probabilities. However, most WLAN stations are equipped with auto-rate adjustment techniques which are designed to keep the link error rate within a certain range (e.g., by varying the transmit rate). By way of example, 802.11b systems may be configured to switch between 11 Mbps, 5.5 Mbps, 2 Mbps and 1 Mbps while keeping the link error rate within generally 10%. This rate-adaptation is advantageous because if link error rates (e.g., packet error rates) are allowed to go beyond 10-20%, there is typically found to be noticeable degradation in perceived performance.
Generally speaking, low-rate stations have higher impact on net throughput than high-rate stations. Thus, the net throughput of a wireless system can be, e.g., determined by the lowest rate user. If it is assumed that in a WLAN system stations are distributed uniformly across a circular area covering the radio range, then more stations will select low rates, since the number of stations will increase as one moves farther from the center. In brief, the presence of stations that are displaced further away from the AP (and, e.g., potentially having low-rates affecting net system throughput) is unavoidable.
The present inventors have surmised that using more transmit power to compensate for losses (e.g., due to distance) and, thus, increase the rate is not a very practical solution in WLANs due to, inter alia, the transmit power restrictions in place (such as, e.g., in un-licensed 5 GHz band). In addition, in many cases, stations are mobile devices having battery-life constraints, such that using more transmit power is also counterproductive in this respect.
The present inventors have determined that another aspect to be considered in future WLAN systems (such as, e.g., due to the rapid increase in the number and types of devices operating in WLAN bands) is the presence of interferers (such as, e.g., dynamic and/or local interferers). In this regard, in some instances, a good link (e.g., error free or substantially error free) between a station and an AP can become un-reliable for a short period of time due to the presence of, e.g., one or more local interferer. However, due to the local nature of interference, the AP may be able to receive packets successfully from another station, such as, e.g., another mobile device or another link. As an example, if a second station is much nearer to an AP than a first station, it may have a higher received signal power at the AP (e.g., which may be able to withstand the interference).
The present inventors have identified that in an infrastructure WLAN system, a station can essentially address its packets only to the AP. The inventors have further identified that in such an common system, re-routing in the sense of MAC and higher layers is not applicable, and that re-routing in this case needs the presence of multiple physical links (though they may be, e.g., multi-hop)
The present inventors have also identified that range limitations of WLANs, especially such in higher-frequency band (802.11a, 802.11n), is a matter of serious concern. In a typical usage scenarios (such as, by way of example, a multi-floor home, residence or business), where it is difficult for a single AP to reach all areas, there is an unrealized need for smart techniques to extend the wireless reach.
The present inventors have identified that the mere use of ‘repeaters’ which receive the packet and then re-transmit the same creates an undesirable solution. Here, a ‘repeater’ commonly behaves just like another station (e.g., from a MAC layer perspective). Accordingly, repeaters would, thus, increase the medium contention.
While a variety of systems and methods are known, there remains a need for improved systems and methods which overcome one or more of the following and/or other limitations caused by, e.g., the presence of poor links (such as, e.g., low speed and/or unreliable links): 1) low throughput; 2) delays caused interferers (such as, e.g., by local and/or temporal interferers); and/or 3) range limitation.